A compact and reconfigurable silicon nitride time-bin entanglement circuit

Photonic chip based time-bin entanglement has attracted significant attention because of its potential for quantum communication and computation. Useful time-bin entanglement systems must be able to generate, manipulate and analyze entangled photons on a photonic chip for stable, scalable and reconfigurable operation. Here we report the first time-bin entanglement photonic chip that integrates time-bin generation, wavelength demultiplexing and entanglement analysis. A two-photon interference fringe with an 88.4% visibility is measured (without subtracting any noise), indicating the high performance of the chip. Our approach, based on a silicon nitride photonic circuit, which combines the low-loss characteristic of silica and tight integration features of silicon, paves the way for scalable real-world quantum information processors.Comment: 4 pages, 5 figure

Age-Related Decline in Reproductive Sensitivity to Inhibition by Short Photoperiod in Peromyscus Leucopus

Seasonal environments favor the timing, of reproduction to match seasons when Successful reproduction is most likely. Most species of temperate zone mammals suppress reproduction in winter using changes in day length as a cue. In many species, individuals vary genetically in how strongly they respond to these seasonal cues. Individuals also may modify their response to day length depending upon other factors, including their age. Age-specific changes might occur because young, peripubertal rodents are more strongly affected by harsh conditions than adults, and therefore might be more sensitive to inhibitory photoperiods. We tested the hypothesis that genetic variation in responses to photoperiod persists as individuals age. Young males from a captive population of white-footed mice (Peromyscus leucopus) that is genetically variable for reproductive inhibition by short day length (SD) were tested for photoperiod responses. Mice were placed in SD within 3 days after birth, tested at age 70 days, allowed to mature for at least 18 weeks at long day length, and then tested again as adults aged \u3e= 34 weeks. Young males were more likely to be strongly reproductively Suppressed by SD than adults, indicating that age-specific changes in reproductive strategy occur in this Population. However, males that were reproductively photoresponsive when young also were more likely to be reproductively photoresponsive as adults. Thus, genetic tendency for reproductive sensitivity to photoperiod is a trait retained from puberty to adulthood, but attenuates with age

Experimental evidence of stochastic resonance without tuning due to non Gaussian noises

In order to test theoretical predictions, we have studied the phenomenon of stochastic resonance in an electronic experimental system driven by white non Gaussian noise. In agreement with the theoretical predictions our main findings are: an enhancement of the sensibility of the system together with a remarkable widening of the response (robustness). This implies that even a single resonant unit can reach a marked reduction in the need of noise tuning.Comment: 4 pages, 3 figure

The failure of suicide prevention in primary care: family and GP perspectives - a qualitative study

Background Although Primary care is crucial for suicide prevention, clinicians tend to report completed suicides in their care as non-preventable. We aimed to examine systemic inadequacies in suicide prevention from the perspectives of bereaved family members and GPs.Methods Qualitative study of 72 relatives or close friends bereaved by suicide and 19 General Practitioners who have experienced the suicide of patients.Results Relatives highlight failures in detecting symptoms and behavioral changes and the inability of GPs to understand the needs of patients and their social contexts. A perceived overreliance on anti-depressant treatment is a major source of criticism by family members. GPs tend to lack confidence in the recognition and management of suicidal patients, and report structural inadequacies in service provision.Conclusions Mental health and primary care services must find innovative and ethical ways to involve families in the decision-making process for patients at risk of suicide

Multistate Switching of Spin Selectivity in Electron Transport through Light-Driven Molecular Motors

It is established that electron transmission through chiral molecules depends on the electron's spin. This phenomenon, termed the chiral‐induced spin selectivity (CISS), effect has been observed in chiral molecules, supramolecular structures, polymers, and metal‐organic films. Which spin is preferred in the transmission depends on the handedness of the system and the tunneling direction of the electrons. Molecular motors based on overcrowded alkenes show multiple inversions of helical chirality under light irradiation and thermal relaxation. The authors found here multistate switching of spin selectivity in electron transfer through first generation molecular motors based on the four accessible distinct helical configurations, measured by magnetic‐conductive atomic force microscopy. It is shown that the helical state dictates the molecular organization on the surface. The efficient spin polarization observed in the photostationary state of the right‐handed motor coupled with the modulation of spin selectivity through the controlled sequence of helical states, opens opportunities to tune spin selectivity on‐demand with high spatio‐temporal precision. An energetic analysis correlates the spin injection barrier with the extent of spin polarization

Combinatorial Selection Among Geometrical Isomers of Discrete Long-Carbon-Chain Naphthalenediimides Induces Local Order at the Liquid/Solid Interface

We report two families of naphthalenediimides (NDIs) symmetrically functionalized with discrete carbon chains comprising up to 55 carbon atoms (Cn-NDI-Cn, n = 39, 44, 50, and 55) and their self-assembly at the 1-phenyloctane/highly oriented pyrolytic graphite interface (1-PO/HOPG interface). The compounds differ by the presence or absence of two or three internal double bonds in the carbon chains (unsaturated and saturated Cn-NDI-Cn, respectively). Combinatorial distributions of geometrical isomers displaying either the E- or Z-configuration at each double bond are obtained for the unsaturated compounds. Analysis of the self-assembled monolayers of equally long unsaturated and saturated Cn-NDI-Cn by scanning tunneling microscopy (STM) reveal that all Cn-NDI-Cn tend to form lamellar systems featuring alternating areas of aromatic cores and carbon chains. Extended chain lengths are found to significantly increase disorder in the self-assembled monolayers due to misalignments and enhanced strength of interchain interactions. This phenomenon is antagonized by the local order-inducing effect of the internal double bonds: unsaturated Cn-NDI-Cn give qualitatively more ordered self-assembled monolayers compared to their saturated counterparts. The use of combinatorial distributions of unsaturated Cn-NDI-Cn geometrical isomers does not represent a limitation to achieve local order in the self-assembled monolayers. The self-assembly process operates a combinatorial search and selects the geometrical isomer(s) affording the most thermodynamically stable pattern, highlighting the adaptive character of the system. Finally, the antagonistic interplay between the extended carbon chain lengths and the presence of internal double bonds brings to the discovery of the lamellar "phase C" morphology for unsaturated Cn-NDI-Cn with n ≥ 50

The Metallicity-Luminosity Relation, Effective Yields, and Metal Loss in Spiral and Irregular Galaxies

I present results on the correlation between galaxy mass, luminosity, and metallicity for a sample of spiral and irregular galaxies having well-measured abundance profiles, distances, and rotation speeds. Additional data for low surface brightness galaxies from the literature are also included for comparison. These data are combined to study the metallicity-luminosity and metallicity-rotation speed correlations for spiral and irregular galaxies. The metallicity luminosity correlation shows its familiar form for these galaxies, a roughly uniform change in the average present-day O/H abundance of about a factor 100 over 11 magnitudes in B luminosity. However, the O/H - V(rot) relation shows a change in slope at a rotation speed of about 125 km/sec. At faster V(rot), there appears to be no relation between average metallicity and rotation speed. At lower V(rot), the metallicity correlates with rotation speed. This change in behavior could be the result of increasing loss of metals from the smaller galaxies in supernova-driven winds. This idea is tested by looking at the variation in effective yield, derived from observed abundances and gas fractions assuming closed box chemical evolution. The effective yields derived for spiral and irregular galaxies increase by a factor of 10-20 from V(rot) approximately 5 km/sec to V(rot) approximately 300 km/sec, asympotically increasing to approximately constant y(eff) for V(rot) > 150 km/sec. The trend suggests that galaxies with V(rot) < 100-150 km/sec may lose a large fraction of their SN ejecta, while galaxies above this value tend to retain metals.Comment: 40 pages total, including 7 encapsulated postscript figures. Accepted for publication in 20 Dec 2002 Ap

Elastic and vibrational properties of alpha and beta-PbO

The structure, electronic and dynamic properties of the two layered alpha (litharge) and beta (massicot) phases of PbO have been studied by density functional methods. The role of London dispersion interactions as leading component of the total interaction energy between layers has been addressed by using the Grimme's approach, in which new parameters for Pb and O atoms have been developed. Both gradient corrected and hybrid functionals have been adopted using Gaussian-type basis sets of polarized triple zeta quality for O atoms and small core pseudo-potential for the Pb atoms. Basis set superposition error (BSSE) has been accounted for by the Boys-Bernardi correction to compute the interlayer separation. Cross check with calculations adopting plane waves that are BSSE free have also been performed for both structures and vibrational frequencies. With the new set of proposed Grimme's type parameters structures and dynamical parameters for both PbO phases are in good agreement with experimental data.Comment: 8 pages, 5 figure

Cross sections and coherence terms for associative ionization of two differently excited Na(3p) atoms

The associative ionization process in thermal Na(3p)-Na(3p) encounters has been studied in a series of crossed-beam experiments where the light polarization of the two laser beams preparing the excited atoms before collision was varied independently. It is shown how in this way maximum possible information for our geometry is extracted about the dependence of the ion formation process on the shape and spatial orientation of the electron clouds of the two approaching atoms, including all coherence terms. The experimental findings are discussed in the light of recent theoretical results for the states of the Na2 molecule. It is concluded that just a few of the possible geometrical approaches are favorable for molecular-ion formation